OK, so maybe there are no rules for style, but this is as close to being a rule as possible: No notch lapels on formalwear. Last time around (left), President Obama made the rounds of the inaugural balls in a notch-lapel dinner jacket so bad that the parent company of Hart Schaffner Marx, who made it, filed for bankruptcy shortly thereafter. This time (middle) it looks like he's wearing the same one, although at least the addition of a pocket square is an incremental improvement.

What you want to go with here is either a shawl collar or a peak lapel, as shown on this Hackett wool/mohair blend (right).